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powerpc: Fix emulation of illegal instructions on PowerNV platform

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Normally, the kernel emulates a few instructions that are unimplemented
on some processors (e.g. the old dcba instruction), or privileged (e.g.
mfpvr).  The emulation of unimplemented instructions is currently not
working on the PowerNV platform.  The reason is that on these machines,
unimplemented and illegal instructions cause a hypervisor emulation
assist interrupt, rather than a program interrupt as on older CPUs.
Our vector for the emulation assist interrupt just calls
program_check_exception() directly, without setting the bit in SRR1
that indicates an illegal instruction interrupt.  This fixes it by
making the emulation assist interrupt set that bit before calling
program_check_interrupt().  With this, old programs that use no-longer
implemented instructions such as dcba now work again.

CC: <stable@vger.kernel.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Paul Mackerras 2013-06-14 20:07:41 +10:00 committed by Benjamin Herrenschmidt
parent 0e37739b1c
commit bf593907f7
2 changed files with 11 additions and 1 deletions
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2
arch/powerpc/kernel/exceptions-64s.S
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@ -683,7 +683,7 @@ machine_check_common:
STD_EXCEPTION_COMMON(0xb00, trap_0b, .unknown_exception)
STD_EXCEPTION_COMMON(0xd00, single_step, .single_step_exception)
STD_EXCEPTION_COMMON(0xe00, trap_0e, .unknown_exception)
STD_EXCEPTION_COMMON(0xe40, emulation_assist, .program_check_exception)
STD_EXCEPTION_COMMON(0xe40, emulation_assist, .emulation_assist_interrupt)
STD_EXCEPTION_COMMON(0xe60, hmi_exception, .unknown_exception)
#ifdef CONFIG_PPC_DOORBELL
STD_EXCEPTION_COMMON_ASYNC(0xe80, h_doorbell, .doorbell_exception)

10
arch/powerpc/kernel/traps.c
View file

@ -1165,6 +1165,16 @@ void __kprobes program_check_exception(struct pt_regs *regs)
exception_exit(prev_state);
}
/*
* This occurs when running in hypervisor mode on POWER6 or later
* and an illegal instruction is encountered.
*/
void __kprobes emulation_assist_interrupt(struct pt_regs *regs)
{
regs->msr |= REASON_ILLEGAL;
program_check_exception(regs);
}
void alignment_exception(struct pt_regs *regs)
{
enum ctx_state prev_state = exception_enter();